Vehicle powertrains generally comprise power unit and power transmission subsystems. Vehicular power transmission subsystems conventionally include a main transmission and an automotive differential gear assembly for differentially driving two drive wheels.
In order to couple power unit efficiency with the variable speed and power demands of a vehicle, a requirement exists for a vehicle powertrain wherein the power unit and the power transmission can be continuously controlled as an integrated unit over the full range of operation so that the performance characteristics of the powertrain can be adaptively and synergistically optimised in response to command inputs from the vehicle driver. A preferred components of such an adaptively controlled vehicle powertrain is a transmission capable of transmitting power at a continuously variable output speed. Such transmissions may be generically described as continuously variable transmissions.
Previously proposed continuously variable transmissions have tended to be complex, unreliable and inefficient at high torque loads. For these and other practical size, weight and cost considerations, previously proposed continuously variable transmissions have typically been ill-suited for use in vehicle powertrains. A requirement accordingly exists for an efficient, compact and reliable continuously variable transmission that is suitable for use is vehicle powertrains.